The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Internal combustion engines combust a fuel and air mixture to produce drive torque. More specifically, air is drawn into the engine through a throttle. The air is mixed with fuel and the air and fuel mixture is compressed within a cylinder using a piston. The air and fuel mixture is combusted within the cylinder to reciprocally drive the piston within the cylinder, which in turn rotationally drives a crankshaft of the engine.
Engine operation is regulated based on several parameters including, but not limited to, intake air temperature (TPRE), manifold absolute pressure (MAP), throttle position (TPS) and engine RPM. With specific reference to the throttle, the state parameters (e.g., air temperature and pressure) before the throttle are good references that can be used for engine control and diagnostic. For example, proper functioning of the throttle can be monitored by calculating the flow through the throttle for a given throttle position and then comparing the calculated air flow to a measured or actual air flow. As a result, the total or stagnation air pressure before the throttle (i.e., the pre-throttle air pressure) is critical to accurately calculate the flow through the throttle. Alternatively, the total pressure and/or static pressure can be used to monitor air filter restriction.
An air filter is often used in an internal combustion engine to remove contamination from the induction air. Over a period of use the air filter can become plugged and restrict the air flow into the engine. This can reduce performance, reduce fuel economy and increase engine emissions. Therefore, it is important to determine whether air flow is restricted as a result of the air filter.
Traditional internal combustion engines include a pre-throttle pressure sensor that directly measures the pre-throttle pressure. Accordingly, a traditional engine system is able to diagnose air flow restriction resulting from an air filter if up-stream and down-stream pressure sensors are available. However, such additional hardware increases cost and manufacturing time, and is also a maintenance concern because proper operation of the sensors must be monitored and the sensors must be replaced if not functioning properly.